Geology Reference
In-Depth Information
According to other scientists, arsenic, which is adsorbed on the iron
hydroxide surface, is released to groundwater under reducing conditions
(Mukherje et al., 2001). They have also argued that detrital pyrite or
arsenopyrite is absent from the aquifer in these areas.
Studies by the CGWB in West Bengal have indicated the presence of
arsenic-free aquifers in the depth range of 200 to 250 m below ground level
which can be tapped by constructing deep tube wells. Mitigation is difficult
given the scale of the problem as well as social and economic factors.
Options include use of deep groundwater (>150 m), use of disinfected
groundwater from dug-wells, rainwater harvesting, and treatment of
contaminated groundwater and surface water.
Groundwater having more than the maximum permissible limit of 1.0 mg/
lit of iron is reported from high rainfall areas in eastern states and northeastern
states. It is attributed to the dissolution of iron oxides in laterites and other
iron bearing minerals. Iron-removal plants are installed at some places to
provide safe drinking water in these areas.
The problem of acid mine drainage especially from high sulphur Tertiary
coals of Assam in northeastern India is quite acute. In this area the problem
is aggravated due to high rainfall of the order of 400 cm/yr. The mine
drainage water is highly acidic (pH = 2.3 to 4.0) and contains more than
3000 mg/lit of sulphate and about 300 mg/lit iron.
Dumping of industrial waste and sewage into surface water-courses cause
widespread pollution resulting in large number of deaths due to water-borne
diseases.
GROUNDWATER AUGMENTATION THROUGH
ARTIFICIAL RECHARGE
The artificial recharge is being practiced for augmentation of groundwater
reservoir and to provide sustainability to groundwater development in India.
The schemes for artificial recharge are being implemented in different
hydrogeological situations by CGWB and many State Groundwater
Departments. A few case studies from different hydrogeological setups are
given herein under:
Basaltic Terrain—Maharashtra
Over-exploitation of groundwater for orange cultivation has depleted the
groundwater resources in parts of Amravati district, Maharashtra.
Hydrogeological studies have brought out that the watershed WR-2 covering
488 km
2
area has surplus monsoon runoff of about 98.9 million cubic metres
(MCM) which can be conserved through simple artificial recharge structures
like percolation tanks and check dams (cement plugs). The efficiency of
these structures constructed at suitable locations with appropriate design in
case of percolation tanks is 91% and for cement plugs 94%. The benefited
